1. Field of the Invention
The present invention relates to a control apparatus for a hybrid vehicle which is driven by an engine and a motor. In particular, the invention relates to technology in energy recovery control, for making a recovery amount by a motor at the time of deceleration of a vehicle appropriately correspond to vehicle operating conditions.
2. Description of the Related Art
Heretofore there is known a hybrid vehicle incorporating a motor in addition to an engine as drive sources for vehicle propulsion.
One type of such a hybrid vehicle is a parallel hybrid vehicle which uses the motor as an assistance drive source for assisting the output from the engine. In this parallel hybrid vehicle, for example at the time of acceleration, the engine is assisted by means of the motor, while at the time of deceleration, various control is carried out such as performing battery charging by deceleration regeneration, so that the electrical energy (hereunder remaining charge) of the battery can be maintained and the requirements of the driver can be met. For example as shown in Japanese Unexamined Patent Application, First Publication No. 7-123509.
In the abovementioned control apparatus for a hybrid vehicle according to one example of the conventional technology, there is known a control which suppresses fuel consumption by stopping fuel supply to the engine, and which improves energy recovery by converting a part of the kinetic energy of the vehicle by regenerative braking by means of the motor into electrical energy, and storing this.
In this case, the control for stopping and reopening the fuel supply to the engine, is executed based on the operating conditions of the vehicle (for example the degree of throttle opening related to the amount of accelerator operation by the driver). However, in a period from the point in time where the operating conditions of the vehicle (for example the degree of throttle opening being fully closed) are such as to determine stopping fuel supply, until the fuel supply is actually stopped, consideration is not given as to whether or not regenerative braking by the motor is being performed. Hence, in this period, there is the possibility of kinetic energy of the vehicle being wastefully consumed. As a result, in operating conditions such as while travelling in a city area where there is frequent changing between acceleration and deceleration, there is the possibility of the remaining charge of the battery (electrical energy) becoming lower than a predetermined tolerance.
The present invention takes into consideration the abovementioned situation with the object of providing a control apparatus for a hybrid vehicle which can improve energy recovery in accordance with operating conditions at the time of vehicle deceleration.
A control apparatus for a hybrid vehicle of the present invention incorporates an engine and a motor as the vehicle drive sources, and a storage unit which converts a part of an output of the engine or kinetic energy of the vehicle into electrical energy by the motor, and stores this. The control apparatus comprises an operating condition detection device which detects an operating condition of the vehicle; a deceleration condition detection device which detects a deceleration condition at a time of deceleration of the vehicle; a fuel supply amount control device which at a time of deceleration of the vehicle detected by the deceleration condition detection device, executes stopping and supply of fuel to the engine corresponding to operating condition of the vehicle; an electric power generation amount control device which at a time of deceleration of the vehicle detected by the deceleration condition detection device, in the case where regenerative braking is performed to convert a part of the kinetic energy of the vehicle into electrical energy by the motor, sets the electric power generation amount which should be recovered by the motor to generate electric power, based on the operating conditions of the vehicle detected by the operating conditions detection device; and a motor control device which performs regenerative braking in accordance with the electric power generation amount set by the electric power generation amount setting device. The electric power generation amount control device has an electric power generation amount setting device which sets in the fuel supply amount control device, a first electric power generation amount for a vehicle operating condition in a deceleration condition of the vehicle at a time of moving from a condition of executing fuel supplying to the engine to condition of stopping fuel supply, and sets in the fuel supply amount control device, a second electric power generation amount for a vehicle operating condition in a deceleration condition of the vehicle at a time of executing stopping of fuel supply to the engine.
According to the abovedescribed control apparatus for a hybrid vehicle, at the time of deceleration of the vehicle detected by a deceleration condition detection device, regenerative braking is performed by the motor in accordance with an electric power generation amount set by an electric power generation amount setting device of an electric power generation amount control device.
That is to say, in a deceleration condition, in a fuel supply amount control device, regenerative braking is executed to satisfy a first electric power generation amount, with respect to a first predetermined operating condition for at the time of moving from a condition of executing fuel supply to an engine, to a stopped condition, and in a deceleration condition, in the fuel supply amount control device, regenerative braking is executed to satisfy a second electric power generation amount, with respect to a second predetermined operating condition for when fuel supply to the engine is stopped.
As a result, at the time of deceleration of the vehicle, regenerative braking by the motor is also performed in the period from a point in time where it is determined to stop fuel supply based on operating conditions of the vehicle such as for example, a degree of throttle opening, an on or off condition of a brake, an engine revolution speed or the like, until the fuel supply is actually stopped. Hence energy recovery can be improved. As a result, it is possible to prevent the remaining charge of the battery from becoming excessively low.
Moreover, for the regeneration amount in this regenerative braking, two different electric power generation amounts (that is, the first and second electric power generation amounts) are set corresponding to the operating conditions at the time of deceleration. Hence the deceleration feeling of the vehicle can be made to appropriately follow the intention of the driver (for example the action of depressing the accelerator pedal), so that drivability can be improved.
The electric power generation amount setting device may set the first electric power generation amount to a larger value than the second electric power generation amount.
In this case, for example at the time of deceleration of the vehicle with the brake off, the regenerative braking is executed to satisfy the first electric power generation amount when the degree of throttle opening is less than a predetermined opening, and the regenerative braking is executed to satisfy the second electric power generation amount when the degree of throttle opening is greater than the predetermined opening, the first electric power generation amount is set to a larger value than the second electric power generation amount.
As a result, regenerative braking can be appropriately performed corresponding to the operating conditions of the vehicle, and energy recovery and drivability can be improved.
The electric power generation amount setting device may set a difference between the first electric power generation amount and the second electric power generation amount so as to increase with a reduction in speed of the vehicle within a predetermined range of the speed.
In this case, by setting for a vehicle speed within a predetermined range, so that the first electric power generation amount is larger than the second electric power generation amount on low vehicle speed side, energy recovery can be even further improved. Moreover, since the effect of the regenerative braking on the deceleration feeling which the driver feels has a greater influence more on the low speed side, the deceleration feeling can be made to even more appropriately follow the intention of the driver, so that drivability can be improved.
The electric power generation amount setting device may correct the first electric power generation amount and the second electric power generation amount in accordance with an operation of a control device which controls the vehicle and an operation of various auxiliary equipment and the like which are driven by the engine.
According to this control apparatus for a hybrid vehicle, the first electric power generation amount and the second electric power generation amount are corrected in accordance with an on or off condition of a control device comprising for example a brake, or for example the on or off condition of various auxiliary equipment such as a compressor of an air-conditioner constituting an air-conditioning system driven by the engine. As a result, appropriate regenerative braking can be performed corresponding to the operating conditions of the vehicle.
The electric power generation amount setting device, in a deceleration condition of the vehicle while moving from a condition of executing fuel supplying to the engine to condition of stopping fuel supply, in a case where the control device is not operated and an accelerator is not depressed, may set so that the regeneration electric power generation amount by the motor becomes the first electric power generation amount.
In this case, by performing appropriate regenerative braking by the motor, also in the period from a point in time where it is determined to stop fuel supply until the fuel supply is actually stopped, energy recovery can be improved.
The electric power generation amount setting device, in a deceleration condition of the vehicle while moving from a condition of executing fuel supplying to the engine to condition of stopping fuel supply, in a case where the control device is operated and the accelerator is not depressed, may set so that the regeneration electric power generation amount by the motor becomes the second electric power generation amount.